Aluminum electrolytic capacitor and rubber seal for same

ABSTRACT

An aluminum electrolytic capacitor includes a capacitor element having lead terminals; an armor case housing the capacitor element; and a rubber seal having a terminal passage hole for the lead terminals drilled therein and mounted on an opening section of the armor case. A hole diameter of a lead wire passage hole is smaller than an outside diameter of an outside lead wire, and a conical guide surface of progressively smaller diameter is formed between a round bar mating hole and the lead wire passage hole within a terminal passage hole. A passage guide part of progressively smaller diameter from a lead wire body is integrally furnished at an end of the outside lead wire so as to have a smaller diameter than the hole diameter of the lead wire passage hole, forming a conical sloped surface having a predetermined angle on a peripheral surface of the passage guide part.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of Ser. No.14/387,619, filed on Sep. 24, 2014, which is National Phase ofInternational Application No. PCT/JP2012/002919 filed Apr. 27, 2012.

TECHNICAL FIELD

The present invention relates to an aluminum electrolytic capacitor and,more particularly, to a technique for inserting a lead terminal througha terminal passage hole of a rubber seal without applying such anexcessively large load as to deteriorate characteristics to a capacitorelement.

BACKGROUND ART

Referring to a sectional view of FIG. 11, an aluminum electrolyticcapacitor includes, as basic components, a capacitor element 1 includinga pair of lead terminals 2, 2. As shown in FIG. 12, the capacitorelement 1 is formed by winding, via not-shown separator paper, in aspiral shape, an anode foil la and a cathode foil 1 b made of aluminummaterial and having the lead terminals 2 attached thereto.

The capacitor element 1 is housed in an armor case 3 having a bottomedcylindrical shape together with a predetermined electrolytic substance.An opening section of the armor case 3 is sealed by a rubber seal 4.Terminal passage holes 5, 5 are drilled in the rubber seal 4. Respectivedistal end portions of the lead terminals 2, 2 are drawn out to theoutside through the terminal passage holes 5, 5.

Actually, the rubber seal 4 is housed in the armor case 3 together withthe capacitor element 1 in a state in which the tip of the rubber seal 4is attached to the lead terminals 2, 2 earlier. The rubber seal 4 ishermetically fixed in the opening section of the armor case 3 bycaulking of a lateral reduction groove 3 a of the armor case 3, which isformed later, and an end edge 3 b of the armor case 3.

Usually, an aluminum case is used as the armor case 3.Isobutylene-isoprene rubber or the like is used as the rubber seal 4.Usually, non-aqueous or aqueous electrolyzed liquid is used as theelectrolytic substance. However, a solid electrolyte is sometimes used.

As shown in FIG. 12, the lead terminal 2 includes a tab terminal 21 andan outside lead wire 22. The tab terminal 21 is made of an aluminummaterial and includes a flat section 21 a press-molded in a battledoreshape and a round bar section 21 b.

The tab terminal 21 of this type can be obtained by cutting an aluminumround bar material at predetermined length and pressing one end side ofthe round bar material. The flat section 21 a is attached to the anodefoil la and the cathode foil lb by caulking needles, welding, or thelike.

Usually, a copper-coated steel wire (CP wire) is used as the outsidelead wire 22. To improve solderability to a circuit board, the outsidelead wire 22 includes a plated layer on the surface. In the case of Pb(lead) free, Sn 100% plating, Sn/Bi (0.5%) plating, or the like ismainly applied to the plated layer.

The outside lead wire 22 is smaller in diameter than the round barsection 21 b of the tab terminal 21 and is welded to an end face of theround bar section 21 b. A welded section of the outside lead wire 22 isdenoted by reference numeral 23.

Incidentally, when the plated layer on the surface is the Sn 100%plating, the plated layer other than the welded section 23 is stable.However, in the welded section 23, Al, An, Cu, Fe, and the like aremixed. When the welded section 23 is exposed to the outside air, stressacts on an Sn layer because of hydration and oxidation reaction of Al.An Sn whisker (a whisker-like crystal substance) 23 a intensely occursand grows.

In the Sn/Bi (0.5%) plating, although the growth of the whisker isrelaxed than that in the Sn 100%, the whisker also occurs. When thegrowth of the whisker is conspicuous, there is a risk that the whiskerscatters on the circuit board and, in the worst case, shirt-circuits anelectronic circuit.

Therefore, in order to suppress the occurrence of the whisker as much aspossible and prevent the scattering of the whisker to the outside, inPatent Documents 1 and 2, as shown in FIG. 13, the applicant proposes tocoaxially connect, as the terminal passage hole 5 of the rubber seal 4,a large-diameter round bar mating hole 51, in which the round barsection 21 b of the tab terminal 21 is fit, and a small-diameter leadwire passage hole 52, through which the outside lead wire 22 isinserted, and set a hole diameter φ2 of the lead wire passage hole 52smaller than an outer diameter 41 of the outside lead wire 22 (φ2<φ1) toshut off the welded section 23 from the outside air.

According to Patent Documents 1 and 2, the scattering to the outside ofthe whisker 23 a that occurs in the welded section 23 is prevented.However, on the other hand, since the hole diameter φ2 of the lead wirepassage hole 52 is smaller than the outer diameter φ1 of the outsidelead wire 22 (φ<φ1), when the outside lead wire 22 is forcibly insertedthrough the lead wire passage hole 52, excessively large stress isapplied to the capacitor element 1. Because of the excessive stress, thecharacteristics of the capacitor element 1 are sometimes deteriorated.

In order to solve this point, Patent Document 3 proposes to form, in thelead wire passage hole of the rubber seal, a funnel-shaped cylindricalbody made of a thin film gradually reduced in diameter toward the outerside of the capacitor.

Patent Document 4 proposes to integrally form, in the lead wire passagehole of the rubber seal, a sealing plug body having a slit for insertingthe lead terminal and draw out the lead terminal to the outside via theslit.

As a technique similar to Patent Document 4, Patent Document 5 proposesto integrally form, in the lead wire passage hole of the rubber seal, asealing plug made of a thin wall for closing the passage hole and drawout the lead terminal to the outside piecing through the sealing plug.

CITATION LIST Patent Documents

Patent Document 1: Japanese Patent Laid-Open No. 2006-295055

Patent Document 2: Japanese Patent Laid-Open No. 2008-10865

Patent Document 3: Japanese Patent Laid-Open No. 2008-251982

Patent Document 4: Japanese Patent Laid-Open No. 2009-212175

Patent Document 5: Japanese Patent Laid-Open No. 2010-161277

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in the case of the invention described in Patent Document 3,there is a problem in that, because of a molding technique for therubber seal, it is difficult to integrally form, in the rubber seal, thefunnel-shaped cylindrical body made of the thin film gradually reducedin diameter toward the outer side of the capacitor and, even if thecylindrical body can be molded, reliability is poor because theperiphery of the lead terminal is sealed by the funnel-shaped thin filmportion.

In the invention described in Patent Document 4, the lead wire is drawnout to the outside via the slit of the sealing plug. In the inventiondescribed in Patent Document 5, the lead terminal is drawn out to theoutside piercing through the sealing plug. Therefore, in bothinventions, there is a problem in that it is difficult to surely sealthe periphery of the lead terminal.

Therefore, it is an object of the present invention to insert the leadterminal through the terminal passage hole of the rubber seal withoutapplying such an excessively large load as to deterioratecharacteristics to the capacitor element and while keeping a state inwhich the lead terminal can be surely shut off from the outside air.

Means for Solving the Problems

In order to solve the problems, the present invention provides analuminum electrolytic capacitor including: a capacitor element formed bywinding, via a separator, an anode foil and a cathode foil both havinglead terminals attached thereto; an armor case having a bottomedcylindrical shape in which the capacitor element is housed together witha predetermined electrolytic substance; and a rubber seal having aterminal passage hole for the lead terminals drilled therein and mountedon an opening section of the armor case, the lead terminal including atab terminal having a flat section and a round bar section and anoutside lead wire having a plated layer on the surface and welded to anend of the round bar section, the terminal passage hole of the rubberseal including a round bar mating hole, in which the round bar sectionof the tab terminal is fit, and a lead wire passage hole coaxial withthe round bar mating hole and smaller in diameter than the round barmating hole, the outside lead wire being inserted through the lead wirepassage hole, and a hole diameter of the lead wire passage hole beingsmaller than an outer diameter of the outside lead wire, the outsidelead wire being forcibly inserted through the lead wire passage hole tobe drawn out to the outside of the armor case, and a welded section ofthe round bar section and the outside lead wire being shut off from theoutside air, wherein

a conical guide surface gradually reduced in diameter is formed betweenthe round bar mating hole and the lead wire passage hole in the terminalpassage hole, the outside lead wire includes a lead wire body larger indiameter than the hole diameter of the lead wire passage hole and apassage guide part integrally connected to a distal end portion of thelead wire body, the passage guide part is formed to be gradually reducedin diameter from the lead wire body to be smaller in diameter than thehole diameter of the lead wire passage hole, and, in the passage guidepart, a substantially conical sloped surface having a predeterminedinclination angle is formed.

In the present invention, it is preferable that, when an inclinationangle of the guide surface with respect to an imaginary plane Xorthogonal to an axis Y passing the terminal passage hole is representedas θa and the inclination angle of the sloped surface is represented asθb, θa<θb.

Preferably, at least the surface of the passage guide part of theoutside lead wire and/or at least the inner surface of the lead wirepassage hole of the rubber seal is coated with low-friction resin.

In this case, it is preferable that coating thickness of thelow-friction resin is 0.3 to 1.5 μm.

As the low-friction resin, polyparaxylene or silicone oil emulsion ispreferably adopted.

When the entire rubber seal is coated with the low-friction resin, theelectrolytic substance in use may be either non-aqueous or aqueouselectrolyzed liquid.

The present invention is suitable for an aluminum electrolytic capacitorin which lead-free tin plating is applied to the outside lead wire and awhisker tends to occur in a welded section of the outside lead wire.

According to a preferred form of the present invention, in preventingthe electrolyzed liquid from being accumulated between the guide surfaceand the welded section, when an inclination angle of the welded sectionwith respect to an imaginary plane X orthogonal to an axis Y passing theterminal passage hole is represented as θc, the guide surface includesan inclined surface having an angle substantially the same as theinclination angle θc.

As a more preferable form, with a boundary set in an intersectionportion of an extended line of an outer diameter surface of the leadwire body and the guide surface in a state in which the lead wire bodyand the lead wire passage hole are set to be coaxial, the guide surfaceincludes a first inclined surface inclined at an angle substantially thesame as the inclination angle θc from the intersection portion to theinner surface of the round bar mating hole and a second inclined surfaceinclined at an angle smaller than the inclination angle θc from theintersection portion to the inner peripheral edge of the lead wirepassage hole.

In preventing the electrolyzed liquid from being accumulated between theguide surface and the welded section, it is preferable that the leadterminals are fit in the terminal passage hole until the lower end ofthe welded section comes into contact with the intersection portion sothat the first inclined surface substantially adheres to the weldedsection.

The present invention also includes a three-terminal type aluminumelectrolytic capacitor including, besides the lead terminalsrespectively attached to the anode foil and the cathode foil, anelectrically neutral dummy terminal not connected to the capacitorelement, a dummy terminal passage hole for the dummy terminal beingfurther drilled in the rubber seal and the dummy terminal and the dummyterminal passage holes being formed the same as the lead terminals andthe terminal passage hole for the lead terminals.

The present invention also includes a rubber seal for an aluminumelectrolytic capacitor including a terminal passage hole through which alead terminal formed by welding an outside lead wire to an end of around bar section included in a tab terminal, the terminal passage holeincluding a round bar mating hole in which the round bar section is fitand a lead wire passage hole coaxial with the round bar mating hole andsmaller in diameter than the round bar mating hole, the outside leadwire being inserted through the lead wire passage hole, and a holediameter of the lead wire passage hole being smaller than an outerdiameter of the outside lead wire, and the outside lead wire beingforcibly inserted through the lead wire passage hole such that a weldedsection of the round bar section and the outside lead wire is shut offfrom the outside air, wherein

a conical guide surface gradually reduced in diameter is formed betweenthe round bar mating hole and the lead wire passage hole in the terminalpassage hole and, when an inclination angle of the welded section withrespect to an imaginary plane X orthogonal to an axis Y passing theterminal passage hole is represented as θc, the guide surface includesan inclined surface having an angle substantially the same as theinclination angle θc.

In the rubber seal, too, with a boundary set in an intersection portionof an extended line of an outer diameter surface of the outside leadwire and the guide surface in a state in which the outside lead wire andthe lead wire passage hole are set to be coaxial, the guide surfaceincludes a first inclined surface inclined at an angle substantially thesame as the inclination angle θc from the intersection portion to theinner surface of the round bar mating hole and a second inclined surfaceinclined at an angle smaller than the inclination angle θc from theintersection portion to the inner peripheral edge of the lead wirepassage hole.

It is preferable that at least the inside of the terminal passage holeis coated with low-friction resin at film thickness of 0.3 to 1.5 μm.

Advantages of the Invention

According to the present invention, the conical guide surface graduallyreduced in diameter is formed between the round bar mating hole and thelead wire passage hole in the terminal passage hole, the passage guidepart gradually reduced in diameter from the lead wire body to be smallerin diameter than the hole diameter of the lead wire passage hole isintegrally formed on the distal end side of the outside lead wire, andthe substantially conical sloped surface having the predeterminedinclination angle is formed in the passage guide part. Therefore, it ispossible to insert the lead terminal through the terminal passage holeof the rubber seal without applying such an excessively large load as todeteriorate characteristics to the capacitor element and while keeping astate in which the lead terminal is surely shut off from the outsideair.

Therefore, in manufacturing the aluminum electrolytic capacitor in whichthe lead-free tin plating is applied to the outside lead wire,occurrence of a whisker in the welded section is suppressed as much aspossible, and, even if the whisker occurs, in preventing scattering ofthe whisker to the outside, the hole diameter of the lead wire passagehole is set smaller than the outer diameter of the outside lead wire,the outside lead wire is forcibly inserted through the lead wire passagehole and drawn out to the outside of the armor case, and the weldedsection of the round bar section and the outside lead wire is shut offfrom the outside air, an yield rate of the manufacturing is improved andit is possible to further improve productivity.

When the inclination angle of the welded section with respect to theimaginary plane X orthogonal to the axis Y passing the terminal passagehole is represented as θc, the inclined surface having the anglesubstantially the same as the inclination angle θc is included in theguide surface. Therefore, an amount of the electrolyzed liquidaccumulated between the guide surface and the welded section greatlydecreases. It is possible to prevent a liquid leak of the electrolyzedliquid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view separately showing an outside lead wire of alead terminal and a terminal passage hole of a rubber seal included inan aluminum electrolytic capacitor of the present invention;

FIG. 2 is an enlarged sectional view showing a main part of FIG. 1;

FIG. 3 is a schematic diagram showing a state in which the outside leadwire of the lead terminal is inserted through the terminal passage holeof the rubber seal;

FIGS. 4(a), 4(b), and 4(c) are actual object photographs showing endshapes of the outside lead wire according to examples 1 to 3 of thepresent invention;

FIGS. 5(a), 5(b), 5(c), 5(d), and 5(e) are actual object photographsshowing end shapes of the outside lead wire as comparative examples 1 to5;

FIG. 6 is a graph of examples 1 to 3 of the present invention andcomparative examples 1 to 5 showing pressure applied to a capacitorelement when the lead terminal is inserted;

FIG. 7 is a sectional view showing a state in which the outside leadwire of the lead terminal is inserted through the terminal passage holeof the rubber seal;

FIG. 8 is a sectional view of a terminal passage hole for explainingpoints to note in setting a guide surface of the terminal passage holeclose to an inclination angle of a welded section;

FIG. 9 is a sectional view of the terminal passage hole showing apreferred embodiment for setting the guide surface of the terminalpassage hole close to the inclination angle of the welded section;

FIG. 10(a) is a plan view showing a rubber seal having three terminalsincluding a dummy terminal and FIG. 10(b) is an A-A line enlargedsectional view of the rubber seal;

FIG. 11 is a schematic sectional view showing a basic configuration ofthe aluminum electrolytic capacitor;

FIG. 12 is a perspective view showing a state in which the lead terminalused in the aluminum electrolytic capacitor is attached to an electrodefoil; and

FIG. 13 is an enlarged sectional view showing, as a conventionalexample, a dimensional relation between a terminal passage hole of arubber seal and an outside lead wire of a lead terminal for whichwhisker measures are taken.

MODE FOR CARRYING OUT THE INVENTION

Next, several embodiments of the present invention are explained withreference to FIG. 1 to FIG. 10(b). However, the present invention is notlimited to the embodiments. Note that, in the embodiments, componentsthat are the same as or may be regarded the same as the conventionalexample explained with reference to preceding FIGS. 11 to 13 are denotedby the same reference numerals and signs.

In FIG. 1 and FIG. 2, only a main part of the present invention isshown. However, referring to FIG. 11 to FIG. 13 as well, like theconventional example explained earlier, an aluminum electrolyticcapacitor of the present invention includes, as basic components, thecapacitor element 1 including the pair of lead terminals 2, 2, the armorcase 3, and the rubber seal 4.

As shown in FIG. 12, the capacitor element 1 is formed by winding, in aspiral shape, via not-shown separator paper, the anode foil 1 a and thecathode foil lb made of the aluminum material having the lead terminal 2attached thereto.

The capacitor element 1 is housed in the armor case 3 having thebottomed cylindrical shape made of the aluminum material together withthe predetermined electrolytic substance. The opening section of thearmor case 3 is sealed by the rubber seal 4. The terminal passage holes5, 5 are drilled in the rubber seal 4. The respective distal endportions of the lead terminals 2, 2 are drawn out to the outside throughthe terminal passage holes 5, 5.

Actually, the rubber seal 4 is housed in the armor case 3 together withthe capacitor element 1 in a state in which the rubber seal 4 isattached to the lead terminals 2, 2 earlier. The rubber seal 4 ishermetically fixed in the opening section of the armor case 3 bycaulking of the lateral reduction groove 3 a of the armor case 3, whichis formed later, and the end edge 3 b of the armor case 3.

As the rubber seal 4, preferably, a rubber material such as vulcanizedIIR (isobutylene-isoprene rubber) or EPT (ethylene propylene rubber) isused. As the electrolytic substance, usually, non-aqueous or aqueouselectrolyzed liquid is used. However, a solid electrolyte may be used.Usually, the capacitor element 1 is housed in the armor case 3 in astate in which the electrolyzed liquid is impregnated.

As shown in FIG. 12, the lead terminal 2 includes the tab terminal 21and the outside lead wire 22. The tab terminal 21 is made of thealuminum material and includes the flat section 21 a press-molded in thebattledore shape and the round bar section 21 b.

The tab terminal 21 of this type can be obtained by cutting an aluminumround bar material at predetermined length and pressing one end side ofthe round bar material. The flat section 21 a is attached to the anodefoil la and the cathode foil lb by caulking needles, welding, or thelike.

Usually, a copper-coated steel wire (CP wire) is used as the outsidelead wire 22. To improve solderability to a circuit board, the outsidelead wire 22 includes a plated layer on the surface. In the case of Pb(lead) free, Sn 100% plating, Sn/Bi (0.5%) plating, or the like ismainly applied to the plated layer.

As shown in FIG. 1 as well, the outside lead wire 22 is smaller indiameter than the round bar section 21 b of the tab terminal 21 and iswelded to an end face of the round bar section 21 b. A welded section ofthe outside lead wire 22 is denoted by reference numeral 23.

As explained above, when the plated layer on the surface is the Sn 100%plating, the plated layer other than the welded section 23 is stable.However, in the welded section 23, Al, An, Cu, Fe, and the like aremixed. When the welded section 23 is exposed to the outside air, stressacts on an Sn layer because of hydration and oxidation reaction of Al.An Sn whisker (a whisker-like crystal substance) 23 a intensely occursand grows.

In the Sn/Bi (0.5%) plating, the growth of the whisker is relaxed thanthat in the Sn 100%, the whisker also occurs. When the growth of thewhisker is conspicuous, there is a risk that the whisker scatters on thecircuit board and, in the worst case, shirt-circuits an electroniccircuit.

In order to suppress the occurrence of the whisker in the welded section23 as much as possible and prevent the scattering of the whisker to theoutside, in the present invention, as the terminal passage hole 5 of therubber seal 4, the large-diameter round bar mating hole 51, in which theround bar section 21 b of the tab terminal 21 is fit, and thesmall-diameter lead wire passage hole 52, through which the outside leadwire 22 is inserted, are coaxially connected and the hole diameter φ2 ofthe lead wire passage hole 52 is set smaller than the outer diameter φ1of the outside lead wire 22 (φ2<φ1) to shut off the welded section 23from the outside air. However, in the present invention, a configurationexplained below is adopted to make it possible to insert the outsidelead wire 22 through the lead wire passage hole 52 of the rubber seal 4without applying such an excessively large load as to deterioratecharacteristics to the capacitor element 1 and while keeping a state inwhich the outside lead wire 22 is surely shut off from the outside air.

Referring to FIG. 2, according to the present invention, besides a leadwire body 221 having an outer diameter φ1 larger than a hole diameter 42of the lead wire passage hole 52, the outside lead wire 22 integrallyincludes a passage guide part 222 to the lead wire passage hole 52 onthe distal end portion side (in FIG. 2, the lower end side) of the leadwire body 221.

Note that, in FIG. 2, a chain line drawn downward from the lead wirebody 221 indicates the conventional outside lead wire not including thepassage guide part 222.

The passage guide part 222 is formed to be gradually reduced in diameterfrom the lead wire body 221 such that a distal end portion (in FIG. 2, alower end portion) 222 a thereof has a diameter φ3 smaller than the holediameter φ2 of the lead wire passage hole 52 (φ3<φ2).

In this embodiment, the distal end portion 222 a having the outerdiameter φ3 of the passage guide part 222 is formed substantially flat.However, a portion above the outer diameter φ3 entering the lead wirepassage hole 52 may be formed in an arcuate shape.

In the present invention, in the passage guide part 222, a conicalsloped surface 223 having a predetermined angle is formed in a portionfrom the distal end portion 222 a having the outer diameter φ3 to thelead wire body 221 having the outer diameter φ1. Consequently, when theoutside lead wire 22 is inserted through the lead wire passage hole 52,first, the sloped surface 223 of the passage guide part 222 comes intocontact with the inner edge of the lead wire passage hole 52.

On the rubber seal 4 side, as the terminal passage hole 5, the round barmating hole 51 having a hole diameter φ4 (φ1<φ4), in which the round barsection 21 b of the tab terminal 21 is fit closely, and the lead wirepassage hole 52 having a hole diameter φ2 (φ3<φ2<φ1) are coaxiallyprovided. However, in the present invention, a conical guide surface 53gradually reduced in diameter from the round bar mating hole 51 side isformed between the round bar mating hole 51 and the lead wire passagehole 52. Note that, when the outer diameter of the round bar section 21b is represented as φ5, the hole diameter φ4 of the round bar matinghole 51 is slightly smaller than the outer diameter φ5 of the round barsection 21 b (φ4<φ5).

With the passage guide part 222 set as a distal end, the outside leadwire 22 is inserted through the lead wire passage hole 52 whileexpanding the lead wire passage hole 52. In that case, in order toprevent a peak load from being applied to the capacitor element 1, whenan inclination angle of the guide surface 53 with respect to theimaginary plane X-X orthogonal to the axis Y-Y passing the terminalpassage hole 5 is represented as θa and an inclination angle of thesloped surface 223 is represented as θb, it is preferable that θa<θb.Note that a creeping distance of the sloped surface 223 is proportionalto the inclination angle θb.

In improving insertability of the outside lead wire 22 through the leadwire passage hole 52, it is also effective to coat the inner surface ofthe lead wire passage hole 52 and the surface of the guide surface 53with low-friction resin such as polyparaxylene or silicone oil emulsionfor improving slippage.

In this case, coating thickness of the low-friction resin is preferably0.3 to 1.5 μm. Note that, if the film thickness is smaller than 0.3 μm,the slippage by the low-friction resin is not sufficiently displayed. Onthe other hand, it is undesirable if the film thickness exceeds 1.5 μmbecause the electrolyzed liquid is likely to leak from between theoutside lead wire 22 and the lead wire passage hole 52. The low-frictionresin may be applied to the outside lead wire 22 side.

When lead-free tin plating is applied to the outside lead wire 22, insuppressing the growth of the whisker 23 a in the welded section 23, itis preferable to form the guide surface 53 to adhere to the weldedsection 23 a.

As shown in FIG. 3, in a state in which the flat section 21 a of thelead terminal 2 is firmly attached to the electrode foils 1 a and 1 b ofthe capacitor element 1 by, for example, the caulking needle, the leadterminal 2 is forcibly inserted into the lead wire passage hole 52 ofthe rubber seal 4 by a pressing force of a press head 60 applied from anupper part of the capacitor element 1. Concerning examples 1 to 3 of thepresent invention shown in FIGS. 4(a), 4(b), and 4(c) and comparativeexamples 1 to 5 shown in FIGS. 5(a), 5(b), 5(c), 5(d), and 5(e),pressure applied to a caulking portion 21 c of the lead terminal 2 wasmeasured. Therefore, an example of the measurement is explained.

Note that, after the distal end portion of the outside lead wire 22projects from the lead wire passage hole 52, the pressing by the presshead 60 is stopped. Instead, the lead terminal 2 is pulled by anot-shown pulling device. Therefore, the pressure applied to thecaulking portion 21 c of the lead terminal 2 is reduced to substantially0.

In this example, in both of examples 1 to 3 of the present invention andcomparative examples 1 to 5, a lead wire (a CP wire) having a diameterof φ0.8 mm was used as the outside lead wire 22. In both of examples 1to 3 of the present invention and comparative examples 1 to 5, the holediameter φ2 of the lead wire passage hole 52 was set to 0.5 mm and theinclination angle θa of the guide surface 53 was set to 30°.

In example 1 of the present invention shown in FIG. 4(a), the outerdiameter φ3 of the distal end portion 222 a of the passage guide part222 was set to 0.3 mm and the inclination angle θb of the sloped surface223 was set to 45°.

In example 2 of the present invention shown in FIG. 4(b), the outerdiameter φ3 of the distal end portion 222 a of the passage guide part222 was set to 0.3 mm and the inclination angle θb of the sloped surface223 was set to 70°.

In example 3 of the present invention shown in FIG. 4(c), the outerdiameter φ3 of the distal end portion 222 a of the passage guide part222 was set to 0.1 mm and the inclination angle θb of the sloped surface223 was set to 70°.

In comparative example 1 shown in FIG. 5(a), the passage guide part 222was not formed and the lead wire having the diameter of φ0.8 mm wasdirectly used. Therefore, an end diameter of the lead wire was φ0.8 mmand the inclination angle θb was 0°.

In comparative example 2 shown in FIG. 5(b), the outer diameter φ3 ofthe distal end portion 222 a of the passage guide part 222 was set to0.6 mm and the inclination angle θb of the sloped surface 223 was set to60°.

In comparative example 3 shown in FIG. 5(c), the outer diameter φ3 ofthe distal end portion 222 a of the passage guide part 222 was set to0.2 mm and the inclination angle θb of the sloped surface 223 was set to15°.

In comparative example 4 shown in FIG. 5(d), the outer diameter φ3 ofthe distal end portion 222 a of the passage guide part 222 was set to0.6 mm and the inclination angle θb of the sloped surface 223 was set to60°.

In comparative example 5 shown in FIG. 5(e), the outer diameter φ3 ofthe distal end portion 222 a of the passage guide part 222 was set to0.6 mm and the inclination angle θb of the sloped surface 223 was set to70°.

On the other hand, on the rubber seal 4 side, as explained above, thehole diameter φ2 of the lead wire passage hole 52 is 0.5 mm. Besides,the hole diameter φ4 of the round bar mating hole 51 is 1.9 mm, axialdirection thickness T1 of the lead wire passage hole 52 is 0.5 mm,height T2 of the guide surface 53 viewed from the inner edge of the leadwire passage hole 52 is 0.4 mm, and a radial direction distance dl ofthe guide surface 53 is 0.7 mm.

Note that the rubber seal 4 is preferably a rubber material having Shorehardness equal to or higher than 80 that cause less scratches. In thisexample, a rubber material having Shore hardness of 84 was used as therubber seal 4.

In Table 1, pressure (gf) of the caulking portion 21 c of the leadterminal 2 measured by a push-pull gauge in examples 1 to 3 of thepresent invention and comparative examples 1 to 5 is shown. In FIG. 6, agraph by measurement data of the pressure is shown. Note that a distancein Table 1 and the graph is set to 0 mm in a place immediately beforethe outside lead wire 22 collides with the lead wire passage hole 52.

TABLE 1 Moving Force (gf/push-pull gauge data) distance ComparativeComparative Comparative Comparative Comparative (mm) example 1 example 2example 3 example 4 example 5 Example 1 Example 2 Example 3 0 0 0 0 0 00 0 0 0.8 250 320 320 300 350 200 140 100 1.2 420 420 450 420 420 210190 120 1.6 530 600 500 210 270 220 220 160 1.8 600 600 320 210 240 240240 170 2.0 700 240 240 210 240 250 240 190 2.2 750 240 240 210 240 250240 210 2.4 110 240 240 210 240 250 240 210 3.2 110 240 240 210 240 250240 210

As it is seen from Table 1 and the graph, the peak pressure is 750 (gf)in comparative example 1, the peak pressure is 600 (gf) in comparativeexample 2, the peak pressure is 500 (gf) in comparative example 3, andthe peak pressure is 420 (gf) in comparative example 4 and comparativeexample 5. The pressure is likely to deteriorate the characteristics ofthe capacitor element 1 when the lead wire is inserted through.

On the other hand, in examples 1 to 3 of the present invention, a peakof the pressure is hardly observed when the lead wire is insertedthrough. In examples 1 and 2 of the present invention, the pressuretransitions at about 220 to 250 (gf). In examples 3 of the presentinvention, the pressure transitions at about 120 to 210 (gf).

Therefore, according to the present invention, it is possible to insertthe lead terminal 2 through the terminal passage hole 5 of the rubberseal 4 without applying such an excessively large load as to deterioratecharacteristics to the capacitor element 1 and while keeping a state inwhich the lead terminal 2 can be surely shut off from the outside air.Note that, in the case of example 3 of the present invention, it islikely that a product main body is hurt by a sharp-pointed shape of thedistal end. Therefore, examples 1 and 2 of the present invention areconsidered to be most preferable.

Incidentally, as shown in FIG. 1, when an inclination angle of thewelded section 23 with respect to the imaginary plane X-X is representedas θc, the inclination angle θc of the welded section 23 is generallyabout 60 to 70°, although depending on the outer diameter φ5 of theround bar section 21 b and the outer diameter φ1 of the outside leadwire 22.

Note that the actual surface of the welded section 23 includes fineunevenness. The inclination angle θc is an angle of a line connecting alower end 23 a and an upper end 23 b of the welded section 23 (the lowerend edge of the round bar section 21 b ) with respect to the imaginaryplane X-X.

On the other hand, when the inclination angle θa of the guide surface 53is set to, for example, 30° as in the example explained above, as shownin FIG. 7, after the lead wire is inserted through, a gap G is formedbetween the guide surface 53 and the welded section 23. Therefore, aproblem explained below occurs.

As explained with reference to FIG. 3, the lead terminal 2 is insertedthrough the terminal passage hole 5 of the rubber seal 4 in a state inwhich the lead terminal 2 is attached to the capacitor element 1. Sincethe electrolyzed liquid is impregnated in the capacitor element 1, apart of the electrolyzed liquid collects in the gap G. Then, theelectrolyzed liquid sometimes gradually leaks from a space between theoutside lead wire 22 and the lead wire passage hole 52.

This problem is solved by setting the inclination angel θa of the guidesurface 53 close to the inclination angle θc of the welded section 23 tonarrow the gap G. In that case, the following points need to be takeninto account.

Referring to FIG. 8, when the outside lead wire 22 is inserted throughthe lead wire passage hole 52 as shown in FIG. 7, the lower end 23 a ofthe welded section 23 collides with an intersection P of the guidesurface 53 and the outer diameter surface of the outside lead wire 22.Therefore, as indicated by an alternate long and two short dashes line,it is conceivable to form the guide surface 53 as an inclined surfacehaving the inclination angle θc passing the intersection P.

However, if the guide surface 53 is formed as the inclined surface, theaxial direction thickness T1 of the lead wire passage hole 52 is shavedby Ta and reduced. Therefore, this is not preferable in hermeticallysealing the outside lead wire 22 and reliability is spoiled.

Therefore, in the present invention, as shown in FIG. 9, with theintersection P set as a boundary, the guide surface 53 is divided intofirst and second two broken line-like inclined surfaces 53 a and 53 bhaving different inclination angles.

That is, the first inclined surface 53 a is formed as an inclinedsurface inclined at an angle (e.g., about 60 to 70°) substantially thesame as the inclination angle θc of the welded section 23 from theintersection P to the inner surface of the round bar mating hole 51. Onthe other hand, the second inclined surface 53 b is formed as aninclined surface inclined at an angle (e.g., about 30°) smaller than theinclination angle θc from the intersection P to the inner peripheraledge of the terminal passage hole 52.

Consequently, it is possible to set the inclination angle of the guidesurface 53 close to the inclination angle θc of the welded section 23and narrow the gap G without reducing the axial direction thickness T1of the lead wire passage hole 52, without hardly shifting an attachmentheight position of the tab terminal 21 to the rubber seal 4 upward inFIG. 7, and without spoiling a guidance effect of the passage guide part222 of the outside lead wire 22 with respect to the lead wire passagehole 52.

The present invention also includes a three-terminal type aluminumelectrolytic capacitor including, as shown in FIG. 10(a), besides thelead terminals 2,2 (see FIGS. 11 and 12) respectively attached to theanode foil la and the cathode foil 1 b, an electrically neutral dummyterminal 30 not connected to the capacitor element 1 is inserted throughthe rubber seal 4.

The dummy terminal 30 is a terminal soldered to a not-shown circuitboard together with the lead terminals 2, 2 solely to improve mountingstability. The dummy terminal 30 is different from the lead terminal 2in that the dummy terminal 30 is larger in diameter than the leadterminal 2 and, as shown in FIG. 10(b), the tab terminal 21 does notinclude the flat section 21 a and includes only the round bar section 21b.

That is, on one end side (in FIG. 10(b), the lower end side) of theround bar section 21 b, the outside lead wire 22 is integrally attachedvia the welded section 23. In this embodiment, on the other end side (inFIG. 10(b), the upper end side) of the round bar section 21 b, a flangesection 31 expanded in diameter is formed.

On the rubber seal 4 side, the terminal passage hole 5 formed bycoaxially connecting the large-diameter round bar mating hole 51, inwhich the round bar section 21 b of the dummy terminal 30 is fit, andthe small-diameter lead wire passage hole 52, through which the outsidelead wire 22 is inserted, is drilled. However, in this embodiment, arecess 54, in which the flange section 31 is closely fit, is formed atthe upper edge of the round bar mating hole 51.

In the three-terminal type aluminum electrolytic capacitor, the holediameter φ2 of the lead wire passage hole 52 of the dummy terminal 30 issmaller than the outer diameter φ1 of the outside lead wire 22 (φ2<φ1)to shut off the welded section 23 from the outside air. However, to makeit possible to insert the outside lead wire 22 through the lead wirepassage hole 52 of the rubber seal 4 without applying such anexcessively large load as to deteriorate characteristics to thecapacitor element 1 and while keeping a state in which the outside leadwire 22 can be surely shut off from the outside air, as in the leadterminal 2, the passage guide part 222 having the sloped surface 223 isintegrally formed at the distal end of the outside lead wire 22. In theterminal passage hole 5, the guide surface 53 for guiding the distal endof the outside lead wire 22 to the lead wire passage hole 52 is formed.

In order to further narrow the gap G (see FIG. 7) between the weldedsection 23 in the dummy terminal 30 and the guide surface 53, asexplained with reference to FIG. 9 above, the guide surface 53 mayinclude the first inclined surface 53 a inclined at an anglesubstantially the same as the inclination angle θc of the welded section23 from the intersection P to the inner surface of the round bar matinghole 51 and the second inclined surface 53 b inclined at an anglesmaller than the inclination angle θc from the intersection P to theinner peripheral edge of the terminal passage hole 52.

In this way, according to the present invention, in the three-terminaltype aluminum electrolytic capacitor including the dummy terminal 30,too, it is possible to insert the outside lead wire 22 through the leadwire passage hole 52 of the rubber seal 4 without applying such anexcessively large load as to deteriorate characteristics to thecapacitor element 1 and while keeping a state in which the outside leadwire 22 can be surely shut off from the outside air and it is possibleto form the gap G between the welded section 23 and the guide surface 53as narrow as possible.

DESCRIPTION OF SYMBOLS

-   1 Capacitor element-   2 Lead terminal-   3 Armor case-   4 Rubber seal-   5 Terminal passage hole-   21 Tab terminal-   21 a Flat section-   21 b Round bar section-   22 Outside lead wire-   221 Lead wire body-   222 Passage guide part-   222 a Distal end portion of the passage guide part-   223 Sloped surface-   23 Welded section-   30 Dummy terminal-   51 Round bar mating hole-   52 Lead wire passage hole-   53 Guide surface-   53 a First inclined surface-   53 b Second inclined surface-   P Intersection

What is claimed is:
 1. An aluminum electrolytic capacitor comprising: acapacitor element formed by winding, via a separator, an anode foil anda cathode foil both having lead terminals attached thereto; an armorcase having a bottomed cylindrical shape in which the capacitor elementis housed together with a predetermined electrolytic substance; and arubber seal having a terminal passage hole for the lead terminalsdrilled therein and mounted on an opening section of the armor case, thelead terminal including a tab terminal having a flat section and a roundbar section and an outside lead wire having a lead-free tin plated layeron a surface and welded to an end of the round bar section, the terminalpassage hole of the rubber seal including a round bar mating hole, inwhich the round bar section of the tab terminal is fit, and a lead wirepassage hole coaxial with the round bar mating hole and smaller indiameter than the round bar mating hole, the outside lead wire beinginserted through the lead wire passage hole, and a hole diameter of thelead wire passage hole being smaller than an outer diameter of theoutside lead wire, the outside lead wire being forcibly inserted throughthe lead wire passage hole to be drawn out to the outside of the armorcase, and a welded section of the round bar section and the outside leadwire being shut off from an outside air, wherein a conical guide surfacegradually reduced in diameter is formed between the round bar matinghole and the lead wire passage hole in the terminal passage hole, theoutside lead wire includes a lead wire body larger in diameter than thehole diameter of the lead wire passage hole and a passage guide partintegrally connected to a distal end portion of the lead wire body, thepassage guide part is formed to be gradually reduced in diameter fromthe lead wire body to be smaller in diameter than the hole diameter ofthe lead wire passage hole, in the passage guide part, a substantiallyconical sloped surface having a predetermined inclination angle isformed, and when an inclination angle of the guide surface with respectto an imaginary plane X orthogonal to an axis Y passing the terminalpassage hole is represented as ea and the inclination angle of thesloped surface is represented as θb, θa<θb.
 2. The aluminum electrolyticcapacitor according to claim 1, wherein an inclination angle of thewelded section with respect to the imaginary plane X orthogonal to theaxis Y passing the terminal passage hole is represented as θc, and witha boundary set in an intersection portion of an extended line of anouter diameter surface of the lead wire body and the guide surface in astate in which the lead wire body and the lead wire passage hole are setto be coaxial, the guide surface includes a first inclined surfaceinclined at an angle substantially the same as the inclination angle θcfrom the intersection portion to an inner surface of the round barmating hole and a second inclined surface inclined at an angle smallerthan the inclination angle θc from the intersection portion to an innerperipheral edge of the lead wire passage hole.
 3. The aluminumelectrolytic capacitor according to claim 2, wherein the lead terminalsare fit in the terminal passage hole until a lower end of the weldedsection comes into contact with the intersection portion so that thefirst inclined surface substantially adheres to the welded section.
 4. Arubber seal for an aluminum electrolytic capacitor comprising a terminalpassage hole through which a lead terminal formed by welding an outsidelead wire to an end of a round bar section included in a tab terminal,the terminal passage hole including a round bar mating hole in which theround bar section is fit and a lead wire passage hole coaxial with theround bar mating hole and smaller in diameter than the round bar matinghole, the outside lead wire being inserted through the lead wire passagehole, and a hole diameter of the lead wire passage hole being smallerthan an outer diameter of the outside lead wire, and the outside leadwire being forcibly inserted through the lead wire passage hole suchthat a welded section of the round bar section and the outside lead wireis shut off from the outside air, wherein a conical guide surfacegradually reduced in diameter is formed between the round bar matinghole and the lead wire passage hole in the terminal passage hole, aninclination angle of the welded section with respect to an imaginaryplane X orthogonal to an axis Y passing the terminal passage hole isrepresented as θc , and with a boundary set in an intersection portionof an extended line of an outer diameter surface of the outside leadwire and the guide surface in a state in which the outside lead wire andthe lead wire passage hole are set to be coaxial, the guide surfaceincludes a first inclined surface inclined at an angle substantially thesame as the inclination angle θc from the intersection portion to aninner surface of the round bar mating hole and a second inclined surfaceinclined at an angle smaller than the inclination angle θc from theintersection portion to an inner peripheral edge of the lead wirepassage hole.